title: Soluble human leukocyte antigen-g5 activates extracellular signal-regulated protein kinase signaling and stimulates trophoblast invasion.
abstract: Soluble human leukocyte antigen-G (HLA-G) is a non-classical class Ib HLA molecule that is secreted from blastocysts. Soluble HLA-G modulates the immune tolerance of the mother and can be used as a prognostic factor for the clinical pregnancy rate. However, the underlying mechanism of how soluble HLA-G5 affects pregnancy remains largely unknown. We hypothesized that soluble HLA-G5 promotes successful implantation and pregnancy by modulating trophoblast invasion through receptor binding and activation of extracellular signal-regulated protein kinase (ERK) signaling pathway. Recombinant HLA-G5 protein over-expressed in E. coli BL21 was purified to near homogeneity. We studied the expression of HLA-G5 and its receptors, the leukocyte immunoglobulin-like receptor subfamily B1 (LILRB1) and killer cell immunoglobulin-like receptor 2DL4 (KIR2DL4), in primary trophoblasts and trophoblastic (JAr and JEG-3) cell lines by florescence-labeled HLA-G5. HLA-G5 was detected in the primary trophoblasts and JEG-3 cells. The LILRB1 and KIR2DL4 receptors were expressed in both primary trophoblasts and trophoblastic cell lines. HLA-G5 stimulated cell invasion (p<0.05) and increased urokinase (uPA) and matrix metalloproteinases (MMPs) transcripts and their activity (p<0.05) in trophoblastic cells. HLA-G5 activated the ERK signaling pathway and induced ERK1/2 phosphorylation in the trophoblastic cell lines. Addition of ERK inhibitors (U0126 and PD98059) nullified the stimulatory effect of HLA-G5 on trophoblastic cell invasion. Taken together, HLA-G5 induced trophoblast invasion by binding to KIR2DL4 and LILRB1, by increasing uPA and MMPs expressions and by activating the ERK signaling pathway.
authors.affiliation: Department of Obstetrics and Gynaecology, Chinese PLA General Hospital, Beijing, China ; Department of Obstetrics and Gynaecology, The University of Hong Kong, Hong Kong SAR, China.
authors.forename: YiFan
authors.initials: Y
authors.lastname: Guo
authors.forename: Cheuk-Lun
authors.initials: CL
authors.lastname: Lee
authors.forename: Kam-Hei
authors.initials: KH
authors.lastname: So
authors.forename: Jing
authors.initials: J
authors.lastname: Gao
authors.forename: William S B
authors.initials: WS
authors.lastname: Yeung
authors.forename: YuanQing
authors.initials: Y
authors.lastname: Yao
authors.forename: Kai-Fai
authors.initials: KF
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D015703:Antigens, CD / Q000378:metabolism; D002460:Cell Line; D002465:Cell Movement / Q000187:drug effects; D005260:Female; D059951:HLA-G Antigens / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D000075362:Leukocyte Immunoglobulin-like Receptor B1; D020935:MAP Kinase Signaling System; D020782:Matrix Metalloproteinases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D011247:Pregnancy; D011485:Protein Binding; D011971:Receptors, Immunologic / Q000378:metabolism; D054345:Receptors, KIR2DL4 / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D014327:Trophoblasts / Q000378:metabolism*; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics / Q000378:metabolism
chemical_list: D015703:Antigens, CD; D059951:HLA-G Antigens; C105299:LILRB1 protein, human; D000075362:Leukocyte Immunoglobulin-like Receptor B1; D010455:Peptides; D011971:Receptors, Immunologic; D054345:Receptors, KIR2DL4; D011994:Recombinant Proteins; D014568:Urokinase-Type Plasminogen Activator; D020782:Matrix Metalloproteinases